Amplified Socio-Economic Impacts of Concurrent or Sequential Drought-Flood Events: Insights from Disaster Databases (1960–2018)

Compound climate and weather extremes have received significant attention in recent years due to the increased risks that they pose to the environment, human societies, and the economy. While prior studies have identified associations between various hazards in disaster databases, investigations focussing on droughts and floods remain rare. In this study, we analyze the impacts of concurrent or sequential drought-flood extremes from two widely used disaster databases: the Emergency Events Database (EM-DAT) and its geocoded version (GDIS), as well as the DesInventar database. The analysis focuses on the period from 1960 to 2018, aligning with GDIS temporal coverage. We define concurrent or sequential hazards as instances where a flood occurs during a drought period or within four months following a drought.  

Our findings for the global extratropics reveal that the economic losses and the number of affected people resulting from the identified drought-flood events are two to eight times higher than those ascribed to isolated droughts or floods, with a confidence interval ranging from two to twelve. Specifically, in DesInventar, the impact ratio (the mean impact of concurrent or sequential events divided by the mean impact of isolated events) for indirectly affected individuals and financial losses is approximately three. In EM-DAT, the impact ratio reaches three for economic damages and eight for affected individuals. Furthermore, the impact ratios are notably higher in the last 30 years of the study period compared to earlier decades, emphasizing the increasing severity of the drought-flood compound events.

These results highlight the amplified negative impacts when droughts and floods occur concomitantly or sequentially, highlighting the need for more robust policies to address their socio-economic risks, particularly under changing climatic conditions.